The World Sudoku Championship (WSC) is an annual international puzzle competition organised by a member of the World Puzzle Federation. The first event was held in Lucca in 2006. National teams are determined by local affiliates of the World Puzzle Federation. The competition typically consists of 100 or more puzzles solved by all competitors over multiple timed rounds, including classic sudoku, variations and other puzzle types, normally followed by a playoff for the top qualifiers to determine a champion. Examples of rounds include the Relay round, where an answer from one puzzle contributes digits to the start of the next sudoku, and the "World Record" round, in which solvers competed to set a Guinness World Record for fastest sudoku solution.